For years, scientists derided Rau. The gulf between the quagga and the zebra was just too wide, they said. As Rau has continued working, many of the doubters have relented. But some still argue that, even if Henry's children look just like quagga, that doesn't mean they'll be quagga. They could fail to exhibit certain behaviors of the original animal—and it'll be hard to tell what's missing because there is little historical record of the quagga's habits.

We'll probably never know whether Rau's quagga is a true genetic match. The genes in Rau's animals cannot be compared directly with those of the stuffed quagga in natural-history museums, because those specimens are too degraded. That's also why quagga can't be cloned, Jurassic Park-style. Cloning might, however, help us save animals currently headed for extinction, such as the Mongolian gazelle, shown here.